Patent GB-379008-A (GB)
Title: Improvements relating to electric circuit breakers and like protective devices
IPC: H01H73/42
Filed: 1931-06-05
Abstract: 379,008. Automatic circuit-breakers. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and RIBER, C. R., 24, Dorville Road, both in London. June 5, 1931, No. 16418. [Class 38 (v).] Switches, quick-break; switches, locking; bases ; contacts.-Pivoted contact-members are connected to a longitudinally-moving setting member by normally-aligned toggles, and the setting member is moved through a further toggle by a rotatable member. One or more electromagnets in the circuit or circuits controlled by the contact members break the toggles on abnormal conditions, and cause the contactmembers to open, a bimetallic element acting on each armature being provided for allowing such armatures to move on small sustained overloads. The dished base 1 is stamped from sheet metal and formed with lugs, as 2, 3, 4, for securing insulating plates carrying the fixed contacts 15, 17 which may be in the same, or separate, circuits. Movable bridging contacts 47, 48 are secured on insulating blocks pivoted between the sides of channelled sections of contact arms 41, 42 which are pivoted at 43, 44 by means of bent-up ears. Springs 49, 50 are anchored between the arms 41, 42 and the end of a reciprocating member 36 guided by a lug 10 on the base 1 and by a hole in a frame 31, Figs. 2 and 3. A pair of toggles 37, 38 and 39, 40 which are always aligned except during the opening movement, transmit the closing force to the arms 41, 42 as the member 36 is moved downwards, the member 36 being linked at 35 to an arm 34 which is rigid on a rotatable shaft 32 and biased anticlockwise by a spring 32b. The shaft 32 carries a pin 32a which is engageable with lost motion by segments formed on the inner face of the operating handle 33. The switch is closed by clockwise rotation of handle 33 which first takes up the lost motion and then drives the shaft 32, stresses the spring 32b, and rotates the arm 34. An adjustabte stop 31a in the bracket 31 determines the overset position of the toggle 34, 35 in which the pressure of springs 49, 50 prevents a light, opening spring 32c from opening the contacts, and the arms 41, 42 bend slightly at the flat part to provide a wiping closure and good contact-pressure. The toggle 34, 35 can be broken manually to open the switch by rotating the handle counterclockwise, the spring 32c between the handle and shaft preferably starting the movement before the segments engage the pin 32a to drive it positively. Both toggles 37, 38 and 39, 40 can be tripped to open the switch by means of a forked member 51 which is slidable on the member 36 under the action of either or both of two armatures of series electromagnets 54, 55 (shown in Fig. 1, without their windings, for convenience), the latter being mounted on stamped brackets 52, 53, Fig. 3. The channelled armatures 56, 57 have bent-up parts, as 56b, to limit their travel and others to serve as anchorages for springs 59 which are also anchored to members 60 pivoted to the armature pivots 56a. The members 60 are extended to engage behind the outer ends of catches 63 which are pivoted in stamped metal brackets 61 on the top of the magnet cores and have extensions 61a carrying seriesconnected, V-shaped, bimetallic elements 65. The latter on moderate sustained overloads, which are insufficient to cause the electromagnets to attract their armatures, bend into engagement with stops 64 on the catches 63, so releasing the members 60 and removing the restraint of the springs 59. An adjustable cam 62 acts on each of the extensions 61a to vary the current value at which the restraint is removed, the electromagnet being then strong enough to attract its armature and trip open the switch. The switch may be locked "off" by means of a shaped member 66 fitting round the handle 33 and sealed under the securing nut of the cover 24. An earthing terminal 28 may be provided.